This heavy-duty locking casement fastener with night vent option. Locking function, fully reversible so can use on left hung or right hung windows. Features a two-position night vent. The arm has two slots in the side, if the handle is moved to engage either of these slots in the staple it allows the window to be marginally open allowing air circulation but retaining full security. Suitable for weather stripped windows. Comes with a 10-year mechanical guarantee. Suitable for domestic use.